1. Field
Example embodiments relate to a substrate alignment device to perform alignment for overlay in an exposure apparatus.
2. Description of the Related Art
A variety of exposure apparatuses may be used to manufacture semiconductor devices and/or liquid crystal display devices. These exposure apparatuses may employ a reticle or a mask provided with a circuit pattern thereon. An image of the circuit pattern may be projected onto a photoresist-coated workpiece (e.g., substrate or wafer) through a projection lens system.
Manufacturing semiconductor devices may require accurate alignment of circuit patterns because it may be necessary to inscribe circuit patterns over circuit pattern(s) that have been formed on a wafer. Therefore, some exposure apparatuses include an aligner to optically detect an alignment mark formed on a wafer. The aligner detects a position of an alignment mark in a fixed coordinate system (e.g., an XY-coordinate system). The coordinate system may designate a position to which the wafer will be moved for alignment.
One method for detecting the alignment mark is a light beam scanning method. The light beam scanning method is a method including focusing a light beam (e.g., a laser beam) on a spot of a wafer, performing relative movement between an alignment mark and the spot to scan the alignment mark on the basis of the spot, and photoelectrically detecting scattered or diffracted light directed from the alignment mark using photo-multipliers and/or photodiodes. A second method is an image forming method including illuminating a region of an alignment mark on a wafer, picking up an image of the alignment mark using a television camera (for example, a Charge Coupled Device (CCD)) to generate a video signal, and processing the video signal to detect a position of the alignment mark.